re to read the buret to 2 decimal places. Record all zeros that you read. you do

Question

re to read the buret to 2 decimal places. Record all zeros that you read. you do four trials, pick your best three and cross out the If Trial 3 Trial 4 Trial Trial 2 Part A Mass of iron salt:OIa Fe(NH4)2(S0a)2 6H2O(s) Moles of Fe2 Moles of KMnO4 Initial buret reading Final buret reading 27.5L 27Om Volume of KMn04 Molarity of KMnO4 Average molarity of KMnO (best three trials) % RAD: (best three trials) Show all your calculations for one of the trials: Show the calculation for the percent relative average deviation (%RAD) for your KMnO4 stand solution: Page 7 Chemistry 125 Laboratory Manual 2016

Explanation / Answer

Part A)

Trial 1,

moles Fe3+ = 1.011 g/392.13 g/mol = 0.0026 moles

moles KMnO4 = 0.0026 moles/5 = 0.000516 moles

volume KMnO4 = 27.5 ml

molarity KMnO4 = 0.000516 moles x 1000/27.5 ml = 0.020 M

Trial 2,

moles Fe3+ = 1.551 g/392.13 g/mol = 0.0039 moles

moles KMnO4 = 0.0039 moles/5 = 0.000791 moles

volume KMnO4 = 27.0 ml

molarity KMnO4 = 0.000791 moles x 1000/27.0 ml = 0.030 M

Average molarity KMnO4 = 0.025 M

%RAD = [(sq.rt.(2.5 x 10^-5 + 2.5 x 10^-5)/2)/0.025] x 100 = 20%

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